Drivers at ride service Uber held a small-scale protest in London on Thursday, angry over pay in a sign of a new challenge for the rapidly expanding taxi app.

Uber, which allows customers to book and pay for a taxi using a smartphone app, has grown rapidly around the world and is valued at over $50 billion (33 billion pounds) but has faced protests, bans and restrictions in a number of cities.

Some drivers working for the San Francisco-based app in the United States have previously protested against the firm which has now angered some in London by raising the commission it takes for many rides from 20 to 25 percent for new drivers.

Founded in 2009, Uber, whose investors include Goldman Sachs and Google, has had to overcome teething problems including legislative hurdles and opposition from traditional taxi drivers who have brought cities such as Paris and Brussels to a standstill.

However this is one of the first times its own drivers have protested against the company.

Outside the firm's London offices, around 40 protesters held placards with slogans such as "Uber 1* rating for greed" and "Uber Xploitation" with many saying the demonstration was about a range of complaints over pay.

"Increasing commission is one way, there have been three fare drops in the last two years is another way and to continue to flood the circuit (with drivers) so that there's instant response is another way," he added.

Uber, which has over 20,000 drivers in London, said in a statement that the increased service fee would bring British drivers into line with rates charged elsewhere and that the majority were happy working for the app.

"Our door is always open to address any issues individuals have," added Tom Elvidge, General Manager of Uber London.

Popular among customers for its low-cost fast service, Uber was ruled legal by Britain's High Court last month but London's transport authority is consulting on plans to force it and others to ensure booking confirmation at least five minutes before a journey starts and allow advanced booking.